To the Editor: Gibson et al provide us with five cases of fatal drug overdose in an article titled “Opioid overdose deaths can occur in patients with naltrexone implants”.1
Three of these people did not have an active naltrexone implant — two of the deaths occurred 6 months after implant insertion (which is the outer limit of the longest duration implant available), and the implant had been removed from the third person.
In one of these, the cause of death was combined non-opioid drug toxicity, including amphetamine and a cocktail of other drugs, where opioids were not present. Obviously, naltrexone, an opioid antagonist, will not protect against non-opioid drug overdose.
That leaves a single fatal opioid overdose in a patient who had an active implant, and in which the cause of death was acute narcotism, where the individual had injected heroin. Here at last is a case study that should be included, and the authors note that the effects of naltrexone can be overcome, and alert us to the danger of using excess heroin to overcome naltrexone blockade.
While . . . [naltrexone] is a potent . . . [opioid] antagonist . . . the blockade produced . . . is surmountable . . . [and] poses a potential risk to individuals who attempt, on their own, to overcome the blockade by administering large amounts of exogenous opioids. Indeed, any attempt by a patient to overcome the antagonism by taking opioids is very dangerous and may lead to a fatal overdose . . . Patients should be told of the serious consequences of trying to overcome the opiate blockade.2
It is also surprising that no denominator is attempted on the number of patients who may have received treatment by implanted naltrexone between 2000 and 2004. This information is available through the Therapeutic Goods Administration, and would have given the reader a clearer ability to evaluate the significance of this single case study. For example, one of the articles they cite reports one fatality in nearly 600 person-years of follow-up,3 giving a very different impression of risk compared with the article by Gibson and colleagues.
- 1. Gibson AE, Degenhardt LJ, Hall WD. Opioid overdose deaths can occur in patients with naltrexone implants. Med J Aust 2007; 186: 152-153. <MJA full text>
- 2. MIMS Australia. MIMS annual. Sydney: CMPMedica Australia Pty Ltd, 2005.
- 3. Hulse GK, Tait RJ, Comer SD, et al. Reducing hospital presentations for opioid overdose in patients treated with sustained release naltrexone implants. Drug Alcohol Depend 2005; 79: 351-357.
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